Why does LTP keep increasing during offseason?

Could someone how the model works in regards to LTP. Up until yesterday I was using an Off-Season improvement rate, and my last BT was 5 months ago. However during the last 2 months, where I have been training 3-5 hr/wk, all low intensity stuff, my LTP has increased 4-5 watts. Why??


If HIE is slowly decreasing and TP is staying constant (or increasing), that would explain how LTP could be increasing. Hard to know without seeing any XPMC data.

Why the long gap?
Not riding enough to tackle a BT workout once a month?

Thanks Hernan!

Looks like the decline in HIE is likely driving the slight upward trend in LTP, given that TP is relatively unchanged.

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What does it feel like when you ride at that LTP?
Normally it’s the point when conversational breathing begins to falter.
It is not your all-day power number.

If you want to experiment, try one of the O/U workouts based on LTP. That should tell you if the number is in the right ballpark.
For example, ride some sets in this one – Xert - Workout Designer (xertonline.com)
Or ride this one in slope mode so you can control the watts – Xert - Workout Designer (xertonline.com)

You would expect LTP to rise some from lots of low intensity work.
According to your chart variation has been minimal over the last two months.
Are you currently set to No Decay?

Was the RAMP test something you imported and rode with EBC in slope mode or something you did elsewhere?
Do you prefer that type of test versus one of the multi-dimensional BT workouts in the library?
What constraints prevent you from performing high intensity workouts indoors?

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Keep in mind Xert does not use a traditional 5-7 zone model. They use a 3-zone strain model –
Sweet Spot, Threshold and Polarized Training … By the Numbers – Xert (baronbiosys.com)
As to whether LTP and LT1 are close, that varies by individual.

The BT workouts in the library are what many users ride indoors to validate their signature if their other activities (Zwift races, hard group rides, HIIT workouts, etc.) aren’t generating BTs on an irregular basis. XATA will warn you every 3 weeks if no BT has been detected in normal activities.
Visit (1) Xert - Workouts (xertonline.com) and search for “breakthrough”.
There are a variety to choose from starting at 30 minutes long (with 10 minutes of actual red zone efforts). They are designed to be ridden using EBC in slope mode with failure expected at one or more points along the way. Sprints should be a spin up, out of the saddle, all-out efforts for at least 5-7 secs until failure.

My guess is your signature will “normalize” once you are riding outdoors again and adding high intensity into the mix. Or start doing that now by selecting a HI workout when predicted form is fresh.
Or, if you don’t agree with the current numbers you can open the last BT activity and use Advanced MPA tab to adjust and save your edited signature. That too will “normalize” moving forward.

Reference –
Breaking Through the Xert Way! – Xert (baronbiosys.com)
What is Advanced MPA? – Xert (baronbiosys.com)

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LT1 doesn’t directly relate to “Zone 2” or wattage. LT1 is just the point at which your muscles begin to accumulate lactic acid. It’s measured with a lab test. It’s possible to tie the results of that lab test to a particular wattage, but it’s kind of pointless because bike fitness improves so rapidly. If you try to use wattage to know when you are at LT1 you will be in the lab every four weeks retesting. It’s more useful to tie LT1 to your heartrate. Heartrate changes slowly over time. Thus, the heartrate at which you achieve LT1 today will likely be the same, or close to the same, at the end of the season and you can use it to train all year without testing anything.

Put another way, if you know your LT1 heartrate, then just make sure you are below that heartrate for the duration of the ride (on an easy day). Ignore the wattage. It’s irrelevant. Sometimes I drift into the so-called “tempo” zone for long periods of time during an easy ride and my heartrate never rises above LT1. I suppose the ‘FTP crowd’ would say I’m more fit than my FTP reflects and that I should retest. Maybe, but who cares? In base phase and on easy days the only thing that’s relevant is whether you are above or below your LT1 heartrate.

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Nice. Yeah! PW:HR metric for the win during base phase.

I’m not completely sure how to use LTP for a practical purpose either. I’m fairly new to Xert, so someone with a much better understanding of the Xert metrics should really answer this. But from what I’ve read, I think LTP is basically the highest wattage you can hold after you blow up. Like, when you are dropped on a really long ride, and you look down at the Garmin, and you’re only putting out 150 watts (which is normally well within your easy endurance range), but your HR is jacked, and you feel like you can’t push any harder, and your going 9 miles per hour … and dear god where is the frickin’ convenience store!

Yeah … not positive, but I think LTP is just the highest power you can dish out when you are completely shattered and have to limp it home.

The part I’m confuse about is how it correlates to LT1. I mean, if you hold any wattage constant for long enough–even a low wattage like LTP–then eventually, you will experience cardiac drift and your heartrate will naturally rise above your LT1. I don’t see how the two relate without considering heartrate, cardiac drift, and ride duration.